Electronic – the difference in this specific breadboard wiring

breadboardledpowervoltagewiring

As an absolute layperson in electronics I just found out that an LED only lights up when connected like in figure 1 but not when connected like in figure 2. And I just don't get why?

I know an LED is a diode and current can only move through it in one direction, but that's the case in both constructions. I don't see a difference in both constructions.

So why does it obviously make a difference?

figure 1 (battery not depicted):
LED is on
figure 2 (battery not depicted):
LED is off

Best Answer

In the second arrangement, both legs of the LED are on the same horizontal row - In breadboards, each set of 5 holes on either side of the board is shorted together.

In other words, your LED's legs are shorted together, no current will flow through it.

See this image of how a breadboard's holes are typically connected internally:

Image (source)

The red thin lines indicate internal connections between the respective holes.

For a more detailed discussion on breadboards see this answer.

Specific to the Fritzing software the images in the question seem to be made in:

Note that as soon as any lead of a component is inserted into a hole in the on-screen breadboard, all the holes that are internally connected get a green indication - That shows that those holes are essentially electrically connected to the occupied hole.

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